But if you count on your tax refund and you're one of the millions getting tax credits to help pay health insurance premiums under President Barack Obama's law, it's not too early.

Here's why: If your income for 2014 is going to be higher than you estimated when you applied for health insurance, then complex connections between the health law and taxes can reduce or even eliminate your tax refund next year.

Maybe you're collecting more commissions in an improving economy. Or your spouse got a better job. It could trigger an unwelcome surprise.

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The danger is that as your income grows, you don't qualify for as much of a tax credit. Any difference will come out of your tax refund, unless you have promptly reported the changes.

Nearly 7 million households have gotten health insurance tax credits, and major tax preparation companies say most of those consumers appear to be unaware of the risk.

"More than a third of tax credit recipients will owe some money back, and (that) can lead to some pretty hefty repayment liabilities," said George Brandes, vice president for health care programs at Jackson Hewitt Tax Service.

Two basic statistics bracket the potential exposure:

The average tax credit for subsidized coverage on the new health insurance exchanges is $264 a month, or $3,168 for a full 12 months.

The average tax refund is about $2,690.

Having to pay back even as little as 10 percent of your tax credit can reduce your refund by several hundred dollars.

Tax giant H&R Block says consumers whose incomes grew as the year went on should act now and contact HealthCare.gov or their state insurance exchange to update their accounts.

They will pay higher health insurance premiums for the rest of this year, but they can avoid financial pain come spring.

"As time goes on, the ability to make adjustments diminishes," warned Mark Ciaramitaro, H&R Block's vice president of health care services. "Clients count on that refund as their biggest financial transaction of the year. When that refund goes down, it really has reverberations."